Towards Scalable, Multivalent Bacterial Vaccines: Developing a Platform for a Polysaccharide and Peptide Epitope Nanoparticle Vaccine

Abstract

The major cause of serious bacterial illness in children is infection by polysaccharide-encapsulated bacteria. Glycoconjugate vaccines have the potential to generate long-term immunity to these bacteria, but current vaccine systems are limited in their ability to generate long-lived T cell dependent immune responses to multiple bacterial serotypes. We propose a platform for a scalable, highly immunogenic, self-adjuvanting polysaccharide-peptide nanoparticle vaccine that can protect against many bacterial serotypes. The platform utilizes Flash NanoPrecipitation (FNP) with block copolymers that are pre-functionalized with bacterial polysaccharides and immunogenic peptides, allowing for the possibility of nanoparticle functionalization with polysaccharides from a number of different serotypes. The objectives of this thesis are 1) to make and purify thiol-functionalized polysaccharides, 2) to use these thiol-functionalized polysaccharides to make polysaccharide-functionalized block copolymers, 3) to make peptide-functionalized block copolymers, and 4) to make nanoparticle formulations to study the effect of polysaccharide and peptide cargo on the FNP process. In order to produce monothiol-functionalized polysaccharides, reductive aminations were conducted with several different reaction conditions to find the set of conditions that afforded the highest level of polysaccharide functionalization. Reductive amination was also successfully employed to produce polysaccharides that could be purified by Fast Protein Liquid Chromatography (FPLC). Polysaccharide- and peptide-functionalized block copolymers were successfully synthesized using maleimide-thiol conjugation chemistry. Polysaccharide- and peptide-functionalized block copolymers were successfully utilized to form polysaccharide- and peptide-functionalized nanoparticles. Mole percent functionalization of the nanoparticle corona with polysaccharide was found to be a statistically significant predictor of particle diameter. A step-down multiple linear regression model indicated that as mole percent nanoparticle corona functionalization with polysaccharide is increased by 1%, nanoparticle mean diameter is predicted to increase by 1 nm. The successful formation of polysaccharide- and peptide-functionalized nanoparticles provides a proof of concept for the proposed vaccine platform using FNP.